The present invention is related to storage media. More particularly, the present invention is related to systems and methods for identifying defective regions on a storage medium.
A typical storage medium includes a number of storage locations where data may be stored. Data is written to the medium within areas designated for user data by positioning a read/write head assembly over the medium at a particular location, and subsequently passing a modulated electric current through the head assembly such that a corresponding magnetic flux pattern is induced in the storage medium. To retrieve the stored data, the head assembly is positioned over a track containing the desired information and advanced until it is over the desired data. In this position, the previously stored magnetic flux pattern operates to induce a current in the head assembly. This induced current may then be converted to represent the originally recorded data.
The storage locations on the storage medium are typically arranged as a serial pattern along concentric circles known as tracks. FIG. 1 shows a storage medium 100 with two exemplary tracks 150,155 indicated as dashed lines and written respective distances from an outer perimeter 140. The tracks are segregated by servo data written within wedges 160, 165. These wedges include data and supporting bit patterns that are used for control and synchronization of the head assembly over a desired storage location on storage medium 100. In particular, such wedges traditionally include a preamble pattern followed by a single sector address mark (SAM) as shown by element 110. The SAM is followed by a Gray code, and the Gray code is followed by burst information. It should be noted that while two tracks and two wedges are shown, hundreds of each would typically be included on a given storage medium. Further, it should be noted that a sector may have two or more bursts.
Manufacturing the storage medium includes performing a variety of steps that each must be done in a reasonably homogenous fashion to assure that the storage medium is reliable. For example, some steps include depositing or forming one or more magnetically receptive layers onto an underlying substrate. Where the formed layer is uniform, a consistent susceptibility to magnetic information is expected along with a desired reliability. In contrast, where the layer is not uniform, some regions on the storage medium will exhibit a different degree of susceptibility than others. This varying susceptibility to magnetic information results in an inability to read one or more sectors of the storage medium. These sectors are considered flawed and where possible are not used for storing user data. In some cases, however, such flawed sectors are difficult to identify, and the failure to properly identify the flawed sectors often leads to failure of a manufactured drive and/or loss of user data that is improperly stored to a flawed sector.
Hence, for at least the aforementioned reasons, there exists a need in the art for advanced systems and methods for reducing the likelihood of storing information to flawed regions of a storage medium.